This invention relates to a device for cleaning and polishing an end surface of an optical fiber, and more particularly to various adaptors that allow the device to interface with a number of different commercially-available, industry-standard fiber optic cable connectors and associated couplings.
The use of fiber optic cable as the transmission medium for information has become increasingly prevalent. Fiber optic cable has a number of advantages over the well-known electrical wire transmission schemes, such as coaxial cable for video signals and twisted-pair wiring for data transmission. Included among the advantages are low-loss, low-cost, high-bandwidth, transmission security and a larger number of data paths per circular area of the transmission medium. The low-loss characteristic allows data to be transmitted over greater distances before the signal must be amplified by "booster" equipment. Perhaps the biggest advantage of fiber optic cables over electrical wire, though, is the higher integrity of the transmitted information due to the immunity of the fiber optic cable from electromagnetic interference.
Notwithstanding the foregoing, fiber optic cable has its disadvantages. For example, due to the relatively small diameter of the "core" glass portion of the optical fiber strand (e.g., on the order of eight microns for a single mode fiber) within the cable, it is critical that, at a junction or interface between the ends of two fiber optic cables, the transmission axis (i.e., the core) of each optical fiber strand be in precise alignment with one another. This is to ensure that all of the light energy propagating within the core of one strand is transferred to the core of the other strand.
Further, due to the small diameter size of the optical fiber strand (which is defined herein to mean the inner core glass portion together with its surrounding cladding glass portion), the fiber strand is normally encased in an outer protective cable of relatively much large diameter. For example, a single mode fiber has an inner core portion of optically pure glass of a diameter of eight microns, surrounded by a cladding portion of less pure glass of a diameter of 125 microns. Surrounding the cladding may be several outer concentric layers, including a silicone coating surrounding the cladding, followed by a buffer jacket. Next may be a concentric layer of strength members, followed by an outer polyurethane jacket. All of the outer concentric layers following the cladding are referred to hereinafter collectively as the outer cable or jacket. The diameter of the outer cable may approach 4.5 mm. The outer cable aids in the handling of the fiber and also prevents the fiber strand from bending at too sharp of an angle, which could cause breakage of the fiber strand.
At the termination point of the cable (e.g., at a piece of "repeater" equipment that increases or "boosts" the amplitude of the optical signal), the cable is mounted in a connector, which is held in place in a connector receptacle or coupling which may be mounted to a panel of the housing of the booster equipment. A second fiber optic cable is mounted in a corresponding connector that may be held in place in an opposing receptacle or coupling. The optical axis of each fiber strand and corresponding outer cable are ideally in alignment with one another at the interface point of the connector coupling. Alternatively, a light source or receiver may be located on the opposite side of the connector coupling for interface with the fiber optic cable.
However, the interface between the ends of the two optical fiber strands is susceptible to fine dirt and dust particles and grease with the result that the exposed end of one or both optical fiber strands may become contaminated. This can occur when the interface is exposed to the atmosphere for any reason (e.g., when connecting or disconnecting the cables). This can lead to a possible severe degradation in the amount of light energy transferred between the fiber strands. In such case, it is known to disassemble the connector containing the fiber optic cable from the corresponding coupling and either replace it in its entirety or clean the end of the fiber cable with an appropriate cleaning device and associated solution. However, such disassembly is impractical and oftentimes unfeasible, given the nature of the connector, connector coupling and its associated equipment.
In the prior art, it is known to insert a supermarket or medical grade swab, saturated with a cleaning solution, into a receptacle in a connector coupling in an attempt to clean the optical fiber strand. However, such attempts were not always successful because the rod or swab did not always wipe through the center of the optical fiber strand. However, such a conventional method may suffice for cleaning other portions of the end surface of the cable.
As a solution to this problem, U.S. Pat. No. 5,325,452 (hereinafter the '452 patent) describes and claims a device for cleaning and polishing an end surface of an optical fiber. The device comprises a nylon or plastic insert with a hole drilled therethrough. The insert is placed into a receptacle on an industry-standard type (e.g., Model FC) of fiber optic cable connector coupling. A second opposed receptacle on the coupling has inserted therein a fiber optic cable mounted in a connector. The axis of the hole in the insert is eccentric to the fiber core at the center of the fiber optic cable. A cleaning and/or polishing rod is inserted in the insert hole and the rod is rotated. Because of the eccentric axis of the insert hole with respect to the concentric fiber core axis within the fiber optic cable, rotation of the rod allows the end surface of the rod in contact with end surface of the fiber cable to clean through the center of the fiber and, thus, clean the entire end surface of the fiber core.
The intent of the device in the '452 patent is that the insert can be used with any and all of the myriad of styles or models of industry-standard fiber optic cable connectors and corresponding couplings. For sake of clarity, a fiber optic cable connector is defined to be the connector that mounts onto the end of the fiber optic cable. Typically, the outer protective jacket of the fiber cable is removed for a fraction of an inch or so at the end of the fiber optic cable. Then a ferrule, cylindrical in shape, with a hole bored through its center, has the fiber optic core and cladding (i.e., the inner most portions of the cable) inserted into the hole in the ferrule. The connector may also include a rubber boot to provide strain relief for the cable. On the other hand, a coupling is defined as the mechanical interconnecting device into which one or more fiber optic cable connectors are inserted, usually by screwing onto threads or by a bayonet-style connection. Typically, these couplings have a pair of opposed receptacles into which a pair of fiber optic cable connectors are inserted. The opposed receptacles ideally keep the fiber core in each cable in axial alignment with one another.
There exist at least seven industry-standard models of fiber optic cable connectors and corresponding couplings. They are the models ST.RTM., SC, FC, D4, Biconic and SMA, and those used in the aircraft industry. Each of these models of fiber optic cable connectors and coupling has a somewhat different corresponding physical structure. Yet, a cylindrical hole in the coupling that accommodates the ferrule of the fiber optic cable connector is typically constant in diameter for many of the different models. Thus, the leg portion of the insert of the patented device for cleaning and polishing an optical fiber can typically be utilized with several models of the fiber optic cable connectors and/or their corresponding couplings. However, due to the different structure for the couplings, the total design of an insert designed to be utilized, for example, with the Model ST.RTM. fiber optic cable connector and coupling may not be utilized with one or more of the other aforementioned models of couplings. Therefore, up to now, a separate insert had to be designed for each model of connector and coupling. That is, due to structural constraints associated with the fiber optic cable connectors and their associated couplings, no single or "universal" insert could be used for many of the aforementioned models.
In conjunction with the device of the '452 patent, there are occasions when it may be desirable and practical to clean the end surface of an optical fiber strand when the fiber strand mounted in its associated ferrule of the connector is removed from the corresponding coupling. If the insert is designed to be utilized primarily when the fiber optic cable connector is mounted within the coupling, then the insert cannot be used alone when the fiber optic cable connector is disconnected from the coupling. This is because the coupling has a female-type cylindrical receptacle, whereas the ferrule is a male-type device. Yet, for many of the seven aforementioned models of industry-standard fiber optic cable connectors and corresponding couplings, the ferrule may be similar in diameter.
Accordingly, it is a primary object of the present invention to provide, for many of a plurality of different industry-standard fiber optic cable connectors and associated couplings, a corresponding female adaptor or sleeve that allows for proper mechanical interface of a universal insert, which is part of a device for cleaning and polishing an optical fiber, with an optical fiber mounted in the connector that is attached to the associated coupling.
It is another primary object of the present invention to provide, for many of a plurality of industry-standard fiber optic cable connectors used without its associated coupling, a single male-type adaptor that allows for proper mechanical interface of an insert portion of a device for cleaning and polishing an optical fiber with the fiber mounted in the ferrule of the corresponding connector.
It is a general object of the present invention to obviate the need for a separate insert for each of a plurality of industry-standard fiber optic cable connectors and associated couplings.
It is another object of the present invention to provide various adaptors for a plurality of industry-standard fiber optic cable connectors and associated couplings that allows a single device to properly clean and/or polish the end surface of an optical fiber mounted in the connector.
It is yet another object of the present invention to provide various adaptors, both male and female, each adaptor having a concentric hole that adapts a single device for cleaning and polishing an optical fiber having an eccentric hole to a fiber optic cable connector and associated coupling.
It is still another object of the present invention to provide various adaptors for a single device for cleaning and polishing an optical fiber that utilizes an eccentric cleaning motion.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.